Organic phosphorus compounds are used in wide-ranging applications such as ligands in transition metal catalysts and hardening accelerators for epoxy resins. For example, an organic phosphorus compound expressed as 1,2-bis (di-t-butyl phosphinomethyl) benzene is a catalyst ligand that exhibits highly desirable activity in the carbonylation reaction of olefinic unsaturated compounds. Also, an organic phosphorus compound expressed as 2,2′-bis diphenyl phosphanylmethyl-1,1′-biphenyl and derivatives thereof are catalyst ligands that exhibit highly desirable activity and selectivity in the hydroformylation reaction.
Among the key methods for manufacturing such organic phosphorus compounds, methods involving the reaction between a phosphinous chloride and a lithium reagent or Grignard reagent are well known (Patent Literature 1). Also, manufacturing methods using the reaction between a metal phosphide, one representative of which is lithium phosphide, and an electrophile, are also reported (Patent Literatures 2 to 5). However, these methods are not advantageous propositions in industrial applications because preparation of lithium phosphides requires highly hazardous metal lithium and expensive lithium reagents.
Metal phosphides also include synthesized magnesium phosphides, but their examples reported so far are limited to magnesium phosphides containing aromatic groups, such as Ph2PMgBr and PhOcPMgCl (Oc represents an octyl group) (Non-patent Literatures 1, 2). This is because preparing dialkyl magnesium phosphides having primary and secondary straight-chain alkyl groups as substituents is difficult, as the produced dialkyl magnesium phosphide reacts with the dialkyl phosphinous chloride used as a material, which explains why no example of synthesized dialkyl magnesium phosphide, where the phosphorus atom has two substituent alkyl groups, has been reported. Consequently, no manufacturing method of dialkyl phosphine compound has been reported which involves the reaction between a dialkyl magnesium phosphide and an electrophile.
On the other hand, dialkyl or trialkyl phosphine compounds having secondary or tertiary alkyl groups are particularly useful as ligands in transition metal catalysts for cross-coupling reactions, and such compounds of various structures have been proposed. These dialkyl or trialkyl phosphine compounds are generally manufactured by causing a dialkyl phosphinous chloride to react with an organic lithium reagent or Grignard reagent prepared from a halogen compound. There are problems, however, because preparing Grignard reagents from such halogen compounds as benzyl chloride, allyl chloride and cinnamyl chloride is difficult and requires special equipment, while preparation of lithium reagents from halogen compounds requires use of intermediates that contain heavy metals.